HDTV buying guide: Making sense of the specs

Whether you're buying your first HDTV or replacing an older model, you'll find all sorts of new specifications and features to consider when shopping. Some of these apply to both LCD and plasma sets, while others are significant for LED/LCD sets in particular. Here's a quick overview of the different choices and what they may mean for you.

Important specifications for LED/LCD and plasma HDTVs

Resolution: Almost all sets 40 inches or larger have 1080p resolution, which is 1920 by 1080 pixels. A set with 1080p resolution will give you the maximum detail available for almost all HD content. For some smaller HDTV sizes, 1366 by 768 pixels is often a lower-cost choice, but a 720p set has to scale 1080p images down to match its native resolution. This interpolation may introduce imaging artifacts, and the image may not appear quite as sharp or have the depth of the picture on a 1080p set.

While 720p models are available in many sizes as a lower-cost option, they remain prevalent in the 40-inches-or-smaller category. If you're shopping for a small HDTV, expect to pay about a 20 to 25 percent premium (as of this writing) for a 1080p set over a 720p set. All else being equal, we recommend that you pick a 1080p model, which will better match much of the content you can now get from broadcast, streaming, and satellite services, and will match the native resolution of a Blu-ray Disc player.

Contrast: This spec (also known as "contrast ratio") refers to the difference between the darkest images and the lightest images that a screen can produce; in general, it is determined by how dark the blacks are. Contrast is probably the most important factor in determining image quality after resolution. If the blacks are gray and the contrast is lower, the whole image can look washed out. If the blacks are deep and strong, however, the image will look sharper and the colors will pop.

Unfortunately, manufacturers' methods for measuring and specifying contrast are almost useless for helping you predict how the screen will look. Manufacturers use full-screen measurements, all black and all white, in a darkened room. An all-black or all-white screen is not what people watch, and in computer terms it conveys precisely zero bits of information. When you have actual content on the screen, you get internal reflections, ambient lighting effects, and other optical crosstalk that results in the light from one section of an image affecting the light levels of another. Basically, pay attention to the contrast with your eyes, but don't worry about the reported "contrast ratio" spec.

Internet connectivity: These days, most big-brand HDTVs offer the ability to connect to your home network's router--either through a cable or wirelessly--so that you can view content stored on the computers on your network and access content from the Internet if you have broadband service. Different sets have different features, such as Amazon, Netflix, or YouTube, so if you want a particular service, make sure that it's included before you commit to an HDTV--or find a Blu-ray player or streaming set-top box that has the service you want. Manufacturers are adding new services all the time, even to their existing models, so it pays to get the latest information. Note that if you use a wireless connection, 802.11n will give you the fastest performance.

3D support: By now, each of the major manufacturers has a fairly wide range of 3D TVs on the market at various price points. For most prospective TV buyers, 3D isn't a necessity quite yet simply because there isn't enough 3D content out there yet. That said, If you're intrigued by ESPN 3D, building up your 3D Blu-ray collection, or simply want to future-proof your TV, there's a few things you should know about 3D before you pull out your credit card.

Active shutter or passive 3D? There are currently two types of 3D glasses technology found in HDTVs right now, "Active shutter" and "polarized" or "passive". Active-shutter glasses are more expensive (often about $150/pair) and a bit heavier, since they're actually two small LCD screens that alternately dim each "lens" in sync with the TV by way of an infrared emitter so you can see a 3D image. Polarized glasses, on the other hand, are the kind you'll find in 3D movie theaters--in fact, some TVs will even work with the exact same glasses from the theater (which you were supposed to return, by the way). They're cheaper, lighter, and easier to wear, but they technically don't provide as high-quality an image since each lens blocks out some of the light to create the 3D image. So far, however, we haven't seen a significant quality difference between the two 3D technologies--read Active vs. Passive 3D and Do Passive 3D TVs Sacrifice Quality for Comfort? for more information.

What are you going to watch? There isn't much 3D video out there at the moment. Your cable provider might have a channel or two (typically ESPN 3D and a 3D video rental channel), but otherwise you're pretty much limited to what's on the 3D Blu-ray market. Also, keep in mind that 3D TV manufacturers are still scooping up hot 3D Blu-ray movies for their 3D "starter kit" bundles, which means that you can't buy the 3D version of Avatar on Blu-ray without shelling out $230 or so for the two pairs of Panasonic 3D glasses--which won't work with anything but a Panasonic 3D TV.

Don't wait for glasses-free 3D TV. While we've seen some pretty promising prototypes over the years, the fact is that right now, glasses-free 3D is far too expensive and limited to implement in consumer-friendly HDTVs. If you're pondering getting a 3D TV, don't worry about glasses-free 3D TVs coming in a year or two--they're looking like they're at least 5 years, maybe up to 10 years away.

Yes, you can watch 2D TV. The only difference between a 2D and 3D TV is that the 3D model has a display mode that lets you use the included 3D glasses with the TV. You don't need to watch everything with the 3D glasses, though some TVs do support 2D-to-3D upconverting if you want to watch everything in 3D. (The upconverting isn't particularly impressive yet, though.)

HDTV inputs and important buzzwords

Video connections: You have to get the image from your disc player or set-top box into the TV set, and to do so you need to use a video connection. Only three connectors--HDMI, component video, and "VGA"--can deliver HD-resolution images, and of those only HDMI is capable of providing full 1080p HD over an HDCP-protected connection.

HDMI: This is a digital connection, so it delivers the image data exactly as the player or set-top box sends it. HDMI can also carry sound--eliminating the need for extra cables--and it may let you control more than one device with a single click of the remote. The newest version of HDMI is 1.4, which adds more features such as the ability to carry a network connection, but it is not yet available on many devices. HDMI is definitely the connection of choice, as it gives you the most accurate transfer of the image data, and it also supports the HDCP copy-protection features that can help guarantee that you get the best-quality image from your source. One note: Making HDMI cables doesn't involve a lot of magic--a $12 cable bought on the Internet is likely to perform just as well as a $120 cable purchased in some stores. Try a cheap cable first, and if it works, you're done. If it doesn't, you can then try a more expensive cable to see if it solves the problem.

Component video: This connection relies on three separate RCA connectors, marked red, green, and blue. An analog connection, it can handle 1080p signals, but it cannot carry the HDCP copy-protection signal required for some devices. In theory, it may not be as good as a digital connection--especially over a long distance--but you're not likely to notice the difference.

VGA: This label is a misnomer, but it refers to the d-Sub 15 connector that computers use to make an analog connection to a display. In many ways, it's similar to the component video connection. Often it's the easiest way to link a computer to your HDTV. This connection can handle up to 1080p resolution HD.

In addition to those three connectors, you are also likely to find two others: S-Video and composite video. They can carry only standard-definition video images, typically from older devices such as a DVD player, a camcorder, or a VCR. Depending on how you set your HDTV, it can scale standard-def images up to HD (interpolation).

Composite video: This is a single RCA plug, typically yellow. Cables with this plug often also have the standard red and white RCA plugs for stereo audio channels.

How many connections do you need? Most HDTVs today offer at least three HDMI connectors, while many provide four, and some have even more. Get as many HDMI connections as you can; doing so will allow you the most flexibility in attaching devices. For instance, you'll probably want to connect a set-top DVR, a Blu-ray player, a camcorder, or a media streaming box, which links a hard drive and your network to your TV for displaying media content. If possible, use HDMI for your high-definition connections, and try to buy an HDTV that has one more connector than you currently need, to allow for the future expansion of your home entertainment system.

If you have too few HDMI ports on your set, you can always add a switch that will multiply how many devices you can connect to a single input on your HDTV; but this device adds a level of complexity and one more remote control to keep track of.

LED backlight: "LED TVs" are LCD TVs with an LED backlight instead of a standard fluorescent backlight. LEDs consume less power and produce better color response than traditional backlights do, and they also make it possible to create a much thinner LCD TV.

Dynamic backlight or local dimming: Some LCD TVs with LED backlights have the LEDs in a matrix behind the LCD panel, as opposed to other designs that put the LEDs along the edge of the panel to make a thinner TV set. It is possible to turn the LEDs in some sections down or even off, independently of the rest of the backlight. This means that the set can lower the backlight for portions of an image that are dimmer and do not need the backlight's full power. The result is that the set can increase the contrast significantly, as well as save energy.

120Hz refresh rate: A set running at the 120Hz rate takes the normal 60 images per second from the video signal and creates an intermediate image between every pair to create 120 images per second. This increase in refresh rate can help reduce motion blurring in LCD TVs.

240Hz refresh rate: Some sets double the 120Hz approach, creating three intermediate images per pair of frames. Other models simply use the 120 frames but flash the backlight two times per frame. Both of these approaches are intended to reduce motion blur even more, but you are not likely to notice the difference.

Energy Star logo: The U.S. Department of Energy and the Environmental Protection Agency jointly operate the Energy Star logo program, which sets energy-consumption standards for appliances and consumer electronics. Manufacturers are eager to promote a TV's energy-efficient status, so it's a safe bet that sets with the Energy Star logo will consume less power than ones without.

Automatic brightness control: This function will adjust the brightness of your set's image depending on the amount of light in the room; it can be a significant power-saving feature.

Automatic volume leveling: This feature will reduce the difference in volume levels, especially between TV programs and their commercials, which tend to be much louder.

VESA mount holes: Many people now hang their flat-panel TVs on the wall, and they often do the installation job themselves instead of hiring someone. Most wall mounts are designed to match the standard VESA hole patterns, so you may find it easier to mount a flat-panel TV that offers one or more of these patterns on its case.